Shaped charge apparatus



ay 17, 1966 M. REYNE 3,251,300

SHAPED CHARGE APPARATUS Original Filed 001;. l, 1962 5 Sheets-Sheet 1 3/ a May/v66 Fey/7e v INVENTOR.

M. REYNE SHAPED CHARGE APPARATUS 5 Sheets-Sheet a,

May 17, 1966 Original Filed Oct. 1, 1962 Mao/v: e Fey/7 e INVENTOR.

May 17, 1966 M. REYNE SHAPED CHARGE APPARATUS 5 Sheets-Sheet 5 Original Filed Oct. 1, 1962 Ma u/vc e Rey/7 e INVENTOR.

United States. Patent 3,251,300 SHAPED CHARGE APPARATUS Maurice Reyne, Bourg-la-Reine, France, assignor to Societe de Prospection Eiectrique Schlumberger, S.A., Paris, France, a corporation of France Continuation of application Ser. No. 227,382, Oct. 1, 1962. This application June 24, 1965, Ser. No. 470,316 9 Claims. (Cl. 102-24) This is a continuation of application Serial No. 227,382, filed October 1, 1962.

This invention relates to completion of wells and more particularly, to apparatus utilizing explosives for completing wells in a manner to increase the flow index for fluid recovery from earth formations.

In the usual well completion, a jet perforating gun is lowered into a well to the required depth and fired. The resulting perforations extend through the steel casing which lines the well bore, the cement annulus in which the cement casing is set, and into the earth formation. Thus, relatively deep, round holes are provided havinga generally conical termination. The ability of such a hole or perforation to pass fluids to or from a formation is commonly measured in terms of a flow index.

To increase the flow index particularly for formations of relatively low permeability, hydraulic fracturing techniques are often utilized in conjunction with perforating, in both cased and uncased wells. However, the round perforations, unless a number of them are fired in the same plane, do not establish a controlled plane of frac-' ture. In an attempt to establish such control, a so-called pin point entry technique has been used wherein the formation is undercut or underreamed at a given depth by cutting a 360 notch with a mechanical cutter or abrasive Hydraulic fluids are then forced under high pressure into the underreamed portions of the formations to fracture them.

Either of such cutting techniques has a number of disadvantages e.g., a relatively long operating time and uncertainty of the depth control. Particularly where selective fracturing by use of sealing balls is to be practiced, the creation of a slot rather than a round hole is disadvantageous. Hence, use of jet perforations in preparation for fracturing is generally preferred.

Accordingly, it is an object of the present invention to provide new and improved apparatus utilizing explosives for completing wells in a manner to increase the flow index for fluid recovery from the earth formations.

It is a further object of the present invention to provide new and improved apparatus for developing distinctive perforations in earth formations.

Another object of the present invention is to provide new and improved perforating apparatus.

Still another object of the present invention is to provide new and improved apparatus for perforating earth formations behind a casing in a well bore to develop a distinctive perforation in a selected preferential plane for promoting fractures in the plane when hydraulic fluids are applied to the perforation.

In accordance with the present invention, apparatus is provided to form a penetration in earth formations or the like with a generally cylindrical forward section and a wedged-shaped or out-of-round termination. The Wedgeshaped termination may be oriented to align with any selected plane. For example, with the orientation of the wedge-shaped termination in a horizontal plane, the intr-oduction of hydraulic fracturing fluids under pressure will cause the earth formations to fracture preferentially along the horizontal plane with lower breakdown pressure than would ordinarily be required by a conventional perforation. If the Wedge-shaped termination is in a vertical plane, the earth formations can be preferentially fractured in the said vertical plane.

Apparatus in accordance with the present invention includes a shaped charge having a container element, an explosive element contained therein and a liner element therefor, the elements being assembled and disposed in a fixed spatial arrangement along a longitudinal axis through said container and the longitudinal axis corresponding to the axis for a perforating jet formed upon detonation of the shaped charge. The elements of the shaped charge which form the leading end of the perforating jet are uniformly arranged relative to the longitudinal axis to form a uniform forward jet portion while the elements of the shaped charge which form the trailing end of the perforating jet are non-uniformly arranged about the longitudinal axis but have symmetry with respect to a given plane thereby to form a non-uniform rearward jet having an oval configuration in cross-section and symmetry with respect to a given plane.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view in longitudinal cross-section through a section ofearth formations, casing and cement which illustrates a typical perforation developed by the present invention;

FIG. 2 is a view taken along line 22 of FIG. 1;

FIG. 3 is a view in cross-section through a prior art shaped charge unit;

FIG. 4 is a crosssectional view taken through a shaped charge embodying the present invention;

FIG. 5 is an end view of the charge of FIG. 4;

FIG. 6 is a plan view of an element of the shaped charge of FIG. 4;

FIG. 7 is an end view of a modified liner construction for the charge of FIG. 4;

FIG. 8 is a view taken along line 8-8 of FIG. 7;

FIG. 9 is a cross-sectional view of another embodiment of the present invention;

FIG. 10 is an end view of the charge of FIG. 9;

FIG. 11 is an end view of a charge similar to that of FIGS. 9 and 10;

FIG. 12 is a view taken along line 12-12 of FIG. 11;

FIG. 13 is a view of a shaped charge apparatus embodying the present invention; and

FIG. 14 is a view in cross-section taken along line 14-14 of FIG. 13.

Reference is now made to FIGS. 1 and 2, which respectively illustrate, in part, a vertical and a horizontal cross-section through earth formations 20, a casing 21 and a column of cement 22. For a better understanding of the present invention, a typical perforation 24 produced by the apparatus of the present invention will be explained first.

As shown in FIGS. 1 and 2, perforation 24 traverses the casing 21, the cement 22 and a portion of the earth formation 20. Perforation 24 has a circular or round opening 27 in the casing and a forward cylindrically shaped entry portion 28 extending along a longitudinal axis 26. The cylindrical section 28 extends through the cement 22 and into the formations a distance indicated by the dimension a. Adjoining the cylindrical section 28 is a terminal end portion 25 which is characterized by a wedge-shaped or out-of-round configuration. End section 25 extends into the formations from the cylindrical section 28 for a distance indicated by the dimension b. The wedge-shaped configuration of the terminal end portion 25 is apparent from the fan-line expansion of the 'formly about a central axis x of the charge.

4 3 perforation in a horizontal plane (FIG. 2), and the inward curving contraction of the perforation toward the central axis 26 in a vertical plane.

It will immediately be obvious to those skilled in the art of fracturing that the described wedge-shaped configuration is extremely desirable for a number of reasons. For example, the round or circular entrance opening 27 in the casing 21 is less detrimental to the strength of the casing in tension than openings with similar areas but other shapes. A round or circular opening also minimizes the loss in power of the flow of the fracturing fluid therethrough. Moreover, the wedge-shaped termination 25 of the penetration 24 significantly decreases the breakdown pressures necessary to fracture formations and finally, the orientation of the wedge-shaped termination 25 can be preselected to predetermine the preferred orientation of a fracture plane in the formations.

Before discussing the apparatus of the present invention, a brief review of a conventional shaped charge will be given in order to highlight the features of the present invention.

In a conventional shaped charge as used in a well bore perforating apparatus, the container 30, as shown in FIG. 3, is a hollow member which is elongated along a central or longitudinal axis 31 which is also coextensive with the axis of the perforating jet when formed. The container 30 generally has a uniform configuration about its central axis 31 with both a cylindrical interior wall surface 32 and an adjoining tapered or conically shaped inner wall surface 33. Tapered wall surface 33 extends from the cylindrical wall surface 32 to an end wall 34 in a rearward end section 35. A detonating explosive means for the shaped charge, such as a blasting cord 36, is located in a groove in the rearward section 35 for detonating a conventional explosive 37 received in the shaped charge container 30. The explosive material 37 is fitted into the interior of the container 30 and has a forward hollow or recessed section 38 which is generally conically shaped.

A complementarily shaped, relatively thin-walled metallic liner 39 constructed of copper, for example, is fitted into the hollow section 38 of the explosive and the metallic liner and container thereby enclose the explosive 37. When the explosive 37 is detonated by the blasting cord 36, the container 30 which is constructed of lead, for example, contains the explosive pressures for a time sufiicient for the pressures to form a perforating jet travelling along axis 31, the pressures causing a uniform collapse of the liner 39 on the axis 31. The collapse of the liner is inwardly toward axis 31, the apex portion 40 of the liner being in, the forward end of the jet and the base portion 41 of the liner being in the rearward end of the perforating jet as it is projected in a forward direction along axis 31. The jet is continuously formed by the progressive collapsing of the liner and is terminated when the end of the base portion 41 of the liner is finally collapsed on the axis 31 to form the trailing end of the jet. Because the liner element, explosive element and container element have a uniform configuration about the central axis 31 of the charge, the perforating jet is substantially cylindrically shaped and forms a substantially cylindrical perforation in the perforated media.

With the foregoing description of a conventional shaped charge in mind, the present invention will be more clearly understood. Turning now to FIGS. 4 and 5, the basic elements of a shaped charge are illustrated, namely a hollow container element 42, an explosive element 43 and liner element 44. In this embodiment of the invention, the container 42 and the explosive 43 are disposed uni- For convenience of description, cartesian coordinate axes x and y and z are used in the drawings, the axes intersecting at an origin 0. Axes x and y, x and z, y and z, respectively define perpendicular planes xy, xz and yz which intersect at the origin 0.

The liner element 44 is formed with an apex portion 45 having a conical and uniform configuration about the central axis x'and a base portion 46 with diametrically opposed identical distortions from a uniform configuration in a perpendicular plane for aifecting the velocity of collapse of the base portion of the :liner. The sections 45 and 46 of the liner 44 meet in the plane yz, and base 50 of the liner is roughly "spaced a distance from the plane yz equal to about one-third of the height of the liner taken along the axis x from its apex to its base. The base portion 46 of the liner is provided with two diametrically opposed sector plates 47 and 48 which may be suitably attached to the liner in complementary recesses therein. Section 46 is illustrated more clearly in FIG. 5 when the sector plates 47 and 48 are shown disposed along the y axis. In FIG. 6, a plan view of a suitable configuration of a sector plate is illustrated.

The sectors 47 and 48 are preferably constructed from a material having a different specific gravity or density than the material of the main portion of the liner. For example, the sectors 47 and 48 can be made of copper while the main liner portion is made from bronze suitably sintered and formed to the desired shape.

When the explosive 43 in the charge is detonated and the shock wave reaches liner sectors 47 and 48, the different densities of the liner sectors in section 46 provide different velocities of collapse of the liner elements in plane y than in plane z so that the speed of the liner collapse in the plane xz is increased relative to the speed of the liner collapse in the plane xy. The differential speed of liner collapse results in the trailing portion of the perforating jet being developed with a generally oval cross-sectional configuration.

The principle of operation of this charge is as follows: When the explosive 43 is detonated at the rearward end of the charge by a blasting cord 51, the explosive or shock wave travels forwardly. Collapse of the liner occurs first at the apex which is propelled outwardly to form the leading end of the perforating jet. As the jet is propelled outwardly from the container, the shock wave of the explosive continues to uniformly collapse the liner into the jet until the liner collapse reaches the plane yz whereupon the liner is non-uniformly collapsed, thespeed of the liner collapse in the planes xz and xy being dissimilar causing the remaining trailing portion of the jet to form with an oval configuration.

As the thus-formed jet enters into the formation, the leading portion of the perforating jet penetrates the casing, the cement, and the formations in that order, and in so doing, the hole or perforation is produced with a cylindrical opening and a cylindrical forward section. The rearward or trailing section of the jet entering into the cylindrical perforation follows through the cylindrical section and because of the oval configuration cuts into the formations along a preferential plane to form a wedge-shaped or out-of-round section. The wedge-shaped section results because the energy of the perforating jet in its trailing portion is substantially extended in a single plane and a resulting cutting action occurs along this plane.

It should be appreciated that a similar effect can be produced by omitting the sectors 47 and 48 leaving the liner with recesses or indentations in the shape of sectors 47 and 48. In this case, the collapse of the liner elements along plane y would be at a greater speed than the collapse of the liner elements along plane 2.

A practical embodiment of the described invention is as follows: the diameter of the cylindical section of the container (or the base of the liner) is 1.375 inches, the liner having a cone angle of 60. The sector plate dimensions in FIG. 6 are as follows: R equals 1.42 inches; r equals 0.63 inch; and a equals 1.575 inches. The sectors have a thickness of 0.016 inch and the liner has a thickness of 0.032 inch.

Referring now to FIGS. 7 and 8, a modified liner configuration is illustrated wherein a conically shaped liner is provided with diametrically opposed attachments 54 and'55 secured to the inner surface of a conical liner 53. Attachments 54 and 55 are crescent shaped and taper inwardly toward the apex of the liner. The liner may be constructed, for example, of sintered bronze or pressed titanium or a well known bi-metallic liner. The attachments 54 and- 55 may, for example, be constructed of a rubber, epoxy or sintered bronze.- It should be appreciated that the liners and attachments may be an integral one-piece construction where a similar material is used throughout.

In the foregoing description of FIGS. 4-6, a shaped charge is described for producing a perforation with a wedge-shaped termination by means of alternating or distorting the wall configuration of a portion of a liner in a shaped charge in a prescribed manner to delay the collapse of the liner elements along one axis relative to the speed of collapse of the liner elements along a perpendicular axis. FIGS. 7 and 8 illustrate another form the liner may take. The same type of perforation may be produced by altering or distorting the configuration of the container.

Referring now to FIGS. 9-10, another embodiment of the invention is disclosed where a hollow container 60 is uniformly shaped about an x axis and has a parabolically shaped interior wall 61. The explosive is received in the container and has a parabolic recess into which a liner 65 is complementarily fitted. A closure cap 66 is provided for the container.

To develop a non-uniform effect in the trailing portion of a perforating jet, the uniform configuration of the container is altered by diametrically opposed recesses 62, 63 made in the interior wall 61 which are disposed along a y axis and near the base portion of the liner. The recesses 62, .63 thus permit additional explosive materials to be disposed on diameterical sides of the containernear the base portion of the liner and along the y axis thereby to form the trailing portion of the jet with an oval cross-sectional configuration, while the uniform configuration about the apex portions of the liner forms a uniform leading portion of the jet. Because of the shallow formed liner, detonation of the explosive 64 by a blasting cord 67 will cause the apex of the liner to form the leading portion of a perforating jet while the additional explosive in recesses 62, 63 will cause the base portions of the liner to collapse faster in the y plane than in the z plane thereby forming the trailing portion of the jet with an oval configuration.

As a perforating jet as described above enters into the formation, the leading portion of the perforating jet penetrates the casing, the cement and the formations in that order, and in so doing, the perforation is produced with a cylindrical opening and a cylindrical forward section. The rearward or trailing section of the jet entering into the cylindrical perforation follows through the cylindrical section and because of the oval configuration, cuts into the formation to form the wedge-shaped terminal section.

Referring now to FIGS. 11 and 12, a shaped charge 69 is illustrated which is similar to the shaped charge of FIGS. 9 and 10 but has a conically shaped liner 7t). Diametrically opposed recesses 71 and 72 are provided in the walls of the container 73 and located near the base 74 of the liner 70. Hence, the increased explosive load in the palne xy near the base portions of the liner provide for a greater speed of collapse of the liner elements in that plane than the speed of collapse of the liner elements in plane xz with a resulting trailing portion of the perforating jet having an oval configuration while the leading portion of the jet is substantially cylindrical. The

charge 69 operates in a similar manner to the shaped Y charge of FIGS. 9 and 10.

therefor. The explosive materials are coupled to a central blasting cord 83 in the center'of the housing by suitable passageways and covers 84 are provided for each of the cavities. The cavities 77-79 are respectively provided with diametrically opposed identical recesses 85 (only one shown) which lie in longitudinally extending planes so that the wedge-shaped perforation therefor lies in a horizontal plane. Conventional means are provided for detonating the blasting cord 83.

The apparatus 75 can be made of non-porous cast iron which will fragment easily upon detonation of the explosive materials 80. With the shallow depth liner 81, a relatively large entrance hole is produced in the penetrated media.

From the foregoing description it will be appreciated that, in accordance with the present invention, a single shaped charge is provided to sequentially produce a perforation having a forward cylindrical section and a terminating, wedge-shaped or out-of-round section. In the shaped charge, a portion of the charge is arranged to produce a perforating jet having a leading section of explosive energy with a substantially cylindrical uniform configuration and a trailing section of explosive energy with an oval configuration. In this trailing section, the velocity or energy in a given plane is increased relative to the energy of the jet in a perpendicular plane to provide a desired wedge-shaped configuration in a perforation. It should be appreciated that the characteristic of a shaped charge to provide a perforating jet with selected cross-sectional configurations at any point along its length is determined by an interaction between the container element configuration, the explosive element configuration, and the liner element configuration. Each of these element configurations may independently be altered to provide the desired cross-sectional configuration. As the above description clearly illustrates, the shape of the perforating jet along itslength can be altered by a given change in any of the recited element configurations. Moreover, two or more of the recited element configurations can be altered in a complementary manner to provide the described perforating jet. With this understanding, it will be appreciated that the shaped charge of the present invention to provide a perforation with a wedge-shaped termination is not limited by a particular form of a given element since any of the recited elements can be adjusted so as to provide the desired perforation.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects .and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corre-' sponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a hollow shaped charge container element formed about said central axis, an explosive element in said container having a recessed portion formed about said central axis, and a liner element fittedin said recessed portion of said explosive element, said liner element having an apex portion arranged for producing the forward end of a perforating jet relatively uniform about said central axis and a base portion for forming the trailing portion of a perforating jet relatively non-uniform about said central axis, said base portion of said liner having diametrically opposed identical areas along a first plane intersecting said central axis with different characteristic densities as compared to diametrically opposed identical areas of the base portion along a second plane intersecting said central axis and perpendicular to said first plane.

2. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an outof-round recess therebeyond in a media, said shaped charge apparatus comprising: a hollow shaped charge container element formed about said central axis, an explosive element in said container having a recessed portion formed about said central axis, and a liner element fitted in said recessed portion of said explosive element, said liner element having an undistorted apex portion of a constant density around its periphery and uniform configuration arranged for producing the forward end of a perforating jet relatively uniform about said central axis and a base portion for forming the trailing portion of a perforating jet relatively non-uniform about said central axis, said base portion of said liner having diametrically opposed identical attachments along a first plane intersecting said central axis providing increased densities in said first plane as compared to the density of said apex portion and of diametrically opposed base portions disposed along a second plane intersecting said central axis and perpendicular to said first plane.

3. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis correresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a hollow shaped charge container element formed about said central axis, an explosive element in said container having a recessed portion formed about said central axis, and a liner element fitted in said recessed portion of said explosive element, said liner element having an undistorted apex portion of a constant density around its periphery and uniform configuration arranged for producing the forward end of a perforating jet relatively uniform about said central axis and a base portion for forming the trailing portion of a perforating jet relatively non-uniform about said central axis, said base portion of said liner having diametrically opposed identical inserts .along a first plane intersecting said central axis providing increased densities in said first plane .as compared to the density of said apex portion and of diametrically opposed base portions disposed along a second plane intersecting said central axis and perpendicular to said first plane.

4. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis correresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a hollow shaped charge container element formed about said central axis, an explosive element in said container having a recessed portion formed about said central axis, and a liner element fitted in said recessed portion of said explosive element, said liner element having an undistorted apex portion of a constant density around its periphery and uniform configuration arranged for producing the forward end of a perforating jet relatively uniform about said central axis and a base portion for forming the trailing portion of a perforating jet relatively non-uniform about said central axis, said base portion of said liner having diametrically opposed identical recesses along a first plane intersecting said central axis providing different densities in said first plane as compared to the density of said apex portion and of diametrically opposed base portions disposed along a second plane intersecting said central axis and perpendicular to said first plane.

5. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a

hollow shaped charge container element formed about said central axis, an explosive element in said container having a recessed portion formed about said central axis, and a liner element having an apex and a base portion, said liner being fitted into said recessed portion of said explosive element, said container element having diametrically opposed substantially identical recesses therein disposed adjacent to the base of said liner element and terminating forwardly of said apex so that the detonation of said explosive element causes the apex portion of said liner to form the leading portion of a perforating jet with a uniform configuration about said central axis and causes said base portion to form the trailing portion of a perforating jet with an oval configuration.

6. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a hollow shaped charge container element, an explosive element in said container having a recessed portion, and a liner element having apex and base portions, said liner being fitted into said recessed portion of said explosive element, said container element having diametrically opposed substantially identical recesses therein disposed intermediate of the base and apex portions of said liner element so as to form a perforating jet with a leading portion of uniform configuration about said central axis and a trailing portion of non-uniform configuration about said central axis.

7. Shaped charge apparatus having a central axis, said Shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a housing having equiangularly spaced cavities, an explosive element in each of said cavities each of said explosive elements having a recessed portion, and a liner element fitted into each of said recessed portions of said explosive elements, cover means for said cavities, said cavities further including diametrically opposed substantially identical recesses therein disposed intermediate of the base and apex portions of said liner element so as to form a perforating jet with a leading portion of uniform configuration about said central axis and a trailing portion of nonuniform configuration about said central axis.

8. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a housing having equiangularly spaced cavities, an explosive element in each of said cavities each of said explosive elements having a recessed portion, and a liner element fitted into each of said recessed portions of said explosive elements, cover means for said cavities, said base portions of said liners further having diametrically opposed identical areas with different characteristic densities along a first plane intersecting said central axis, as compared to identical diametrically opposed base portions of the'liner disposed along a second plane intersecting said central axis and perpendicular to said first plane.

9. Shaped charge apparatus having a central axis, said shaped charge being arranged for producing, when detonated, a perforating jet along a perforating axis corresponding to said central axis, said perforating jet being arranged to provide a perforation having a characteristic round opening and an out-of-round recess therebeyond in a media, said shaped charge apparatus comprising: a hollow shaped charge container element, an explosive element in said container having a recessed portion, and a liner element having apex and base portions, said liner element being fitted into said recessed portion of said explosive element, said liner, explosive and container elements having a uniform configuration about the apex of said liner to provide, when the explosive element is detonated, a uniform forward jet portion, one of said liner and container elements having diametrically opposed identical distortions along a first plane intersecting said central axis relative to a uniform configuration in a sec- 0nd plane perpendicular to said first plane and intersecting said central axis for affecting the velocity of collapse of the base portions of the liner thereby to form a nonuniform rearward jet portion having an oval con- 15 BENJAMIN A. BORCHELT, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

1. SHAPED CHARGE APPARATUS HAVING A CENTRAL AXIS, SAID SHAPED CHARGE BEING ARRANGED FOR PRODUCING, WHEN DETONATED, A PERFORATING JET ALONG A PERFORATING AXIS CORRESPONDING TO SAID CENTRAL AXIS, SAID PERFORATING JET BEING ARRANGED TO PROVIDE A PERFORATION HAVING A CHARACTERISTIC ROUND OPENING AND AN OUT-OF-ROUND RECESS THEREBEYOND IN A MEDIA, SAID SHAPED CHARGE APPARATUS COMPRISING: A HOLLOW SHAPED CHARGE CONTAINER ELEMENT FORMED ABOUT SAID CENTRAL AXIS, AN EXPLOSIVE ELEMENT IN SAID CONTAINER HAVING A RECESSED PORTION FORMED ABOUT SAID CENTRAL AXIS, AND A LINER ELEMENT FITTED IN SAID RECESSED PORTION OF SAID EXPLOSIVE ELEMENT, SAID LINER ELEMENT HAVING AN APEX PORTION ARRANGED FOR PRODUCING THE FORWARD END OF A PERFORATING JET RELATIVELY UNIFORM ABOUT SAID CENTRAL AXIS AND A BASE PORTION FOR FORMING THE TRAILING PORTION OF A PERFORATING JET RELATIVELY NON-UNIFORM ABUT SAID CENTRAL AXIS, 